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Xiuyun Wu, Austin Rothwell, Miriam Spering, Anna Montagnini; Opposite effects of expectation on motion perception and anticipatory pursuit eye movements. Journal of Vision 2020;20(11):567. doi: https://doi.org/10.1167/jov.20.11.567.
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© ARVO (1962-2015); The Authors (2016-present)
Smooth pursuit eye movements and visual motion perception rely on the integration of current sensory signals with past experience. Expectation derived from past experience can bias perception and even trigger smooth pursuit in anticipation of target onset (Maus, Potapchuk, Watamaniuk, & Heinen, 2015). However, it is still unclear whether perceptual and pursuit biases are similarly affected by expectation. Here we compare biases in perception and anticipatory pursuit by probing both responses in a direction discrimination task.
Observers (n=9 human adults) viewed random-dot kinematograms (RDKs) under different expectations of motion direction (right/left) while their eye position was recorded (Eyelink 1000). Context trials with high-coherence motion were used to build up a prior expectation of motion direction. Probability of rightward motion differed between blocks (50, 70, and 90%). Interleaved perceptual trials with low-coherence motion (0-15%) probed biases in direction discrimination and anticipatory pursuit magnitude. Observers tracked RDK motion with their eyes and reported perceived direction via button press. In experiment 1, motion coherence in context trials was 100%; in experiment 2 coherence was reduced to 20-30% to control for possible motion aftereffects due to sensory adaptation.
Results showed that anticipatory pursuit was aligned with the expected direction (attraction bias). Perceptual judgments in low-coherence trials followed the direction opposite to the expected direction (repulsion bias). The size of both biases scaled monotonically with direction probability. Reducing motion coherence in context trials in exp. 2 significantly reduced anticipatory pursuit magnitude (e.g., velocity gain F(1,8)=11.61, p=.01). However, reducing coherence did not reduce perceptual bias (F(1,8)=1.44, p=.26), indicating that low-level sensory adaptation is unlikely to be the cause of the opposite bias in perception. We conclude that the repulsion bias in motion direction discrimination might be driven by higher-level processing and integration of motion signals.
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